1. Field of the Invention
The present invention relates to a technique for the mapping of addresses to mass storage devices mounted in a mass storage device mounting system.
2. Brief Description of Related Prior Art
Network computer systems generally include a plurality of geographically separated or distributed computer nodes that are configured to communicate with each other via, and are interconnected by, one or more network communications media. One conventional type of network computer system includes a network storage subsystem that is configured to provide a centralized location in the network at which to store, and from which to retrieve data. Advantageously, by using such a storage subsystem in the network, many of the network""s data storage management and control functions may be centralized at the subsystem, instead of being distributed among the network nodes.
One type of conventional network storage subsystem, manufactured and sold by the Assignee of the subject application (hereinafter xe2x80x9cAssigneexe2x80x9d) under the tradename Symmetrix(trademark) (hereinafter referred to as the xe2x80x9cAssignee""s conventional storage systemxe2x80x9d), includes a plurality of disk mass storage devices (e.g., disk drives) configured as one or more redundant arrays of independent (or inexpensive) disks (RAID). The disk devices are controlled by disk controllers (commonly referred to as xe2x80x9cback endxe2x80x9d controllers/directors) that may communicate (i.e., exchange data and commands) with the disk devices via Small Computer System Interface (SCSI) protocol communication channels. The disk controllers are coupled via a bus system to a shared cache memory resource in the subsystem. The cache memory resource is also coupled via the bus system to a plurality of host controllers (commonly referred to as xe2x80x9cfront endxe2x80x9d controllers/directors). The disk controllers are coupled to respective disk adapters that, among other things, interface the disk controllers to the disk devices. Similarly, the host controllers are coupled to respective host channel adapters that, among other things, interface the host controllers via channel input/output (I/O) ports to the network communications channels (e.g., SCSI, Enterprise Systems Connection (ESCON), or FC based communications channels) that couple the storage subsystem to computer nodes in the computer network external to the subsystem (commonly termed xe2x80x9chostxe2x80x9d computer nodes or xe2x80x9chostsxe2x80x9d).
In the Assignee""s conventional storage system, the disk devices are grouped together into respective sets, and each set of disk devices may be controlled by respective pair of disk controllers. If one of the disk controllers in the respective pair fails, the other (i.e., redundant) disk controller in the pair may assume the duties of the failed disk controller, and thereby permit the set of disk devices to continue to operate, despite the failure of the failed disk controller.
Also in the Assignee""s conventional storage system, the disk devices are placed in respective housings and stored in one or more chassis. The chassis may include a multiplicity of sets of slots for receiving respective housings within which the respective disk devices are placed. The chassis may also include an electrical back plane having a multiplicity of electromechanical connectors. The connectors may be mated with respective electromechanical connectors of the housings to electrically and mechanically couple the disk devices to the chassis.
In general, two types of commercially-available disk devices may be mounted in the chassis used in the Assignee""s conventional storage system: xe2x80x9clow profilexe2x80x9d and xe2x80x9chalf-highxe2x80x9d form factor disk devices. With the exception of their respective heights, a low profile form factor disk device (hereinafter xe2x80x9cLP devicexe2x80x9d) may have identically the same dimensions as a half-high form factor disk device (hereinafter xe2x80x9cHH devicexe2x80x9d). An LP device may have a height of 1 inch; an HH device may have a height of 1.6 inches.
At present, the storage capacity of a HH device may be approximately twice that of a LP device. However, the speed with which data may be read from or written to a HH device may be slower than the speed with which data may be read from or written to a LP device.
Only two types of chassis may be used in the Assignee""s conventional storage system. One type of chassis is configured to receive and mount only LP devices, and the other type of chassis is configured to receive and mount only HH devices. Thus, in the Assignee""s conventional storage system, a single chassis cannot contemporaneously receive and store both LP and HH devices; instead, all of the disk devices stored in a single chassis must have a single form factor (i.e., LP or HH).
This is unfortunate, since, given the above-described relative differences in the capabilities of HH and LP devices, in certain practical applications of a data storage system, it may be desirable to employ in an individual chassis combinations of both HH and LP devices that, when taken together, may permit the overall performance of the system to be improved. Also unfortunately, since an individual chassis used in the Assignee""s conventional data storage system is unable to receive and store disk devices having multiple different form factors, this inherently reduces the design flexibility of the data storage system. Thus, it would be desirable to provide a mass storage device mounting system that may use a single type of chassis that is able to contemporaneously receive and store disk mass storage devices that have different form factors (e.g., receive and store combinations of both HH and LP devices).
Additionally, it has been proposed to replace with FC protocol communication channels the SCSI communication channels that permit communication among the disk devices and disk controllers in the Assignee""s conventional data storage system, in order to increase the speed with which such communication may be performed. According to this proposal, each such FC communication channel may comprise a serial, unidirectional, FC communication ring or loop system.
It would also be desirable to provide a technique that may be used to assign FC communication loop addresses to mass storage devices mounted in one or more of the aforesaid type of chassis (i.e., the chassis that is able to receive and store contemporaneously disk devices having multiple different form factors). It would also be desirable to provide such a technique that would permit a maximum number of mass storage devices to be used in a single such FC loop, and would reduce the possibility that human error and/or addressing conflicts may be introduced into the addresses assigned to the mass storage devices.
In accordance with the present invention, a technique is provided for mapping/assigning addresses to mass storage devices in a mass storage device mounting system that overcomes the aforesaid and other disadvantages of the prior art. More specifically, in one embodiment of the present invention, a method is provided for assigning numerical addresses to mass storage devices mounted in a mass storage device mounting system. The mounting system may be of the type, disclosed in the aforesaid copending U.S. patent application Ser. No. 09/877,808, entitled xe2x80x9cMass Storage Device Mounting System,xe2x80x9d filed concurrently with the subject application. As is disclosed in said copending application, this type of mounting system includes one or more electrical cabinets or chassis, and is able to mount different respective configurations of mass storage devices. Each of the chassis in the mounting system is able to contemporaneously receive and store a respective combination of disk mass storage devices. The respective combination of disk mass storage devices may include both HH and LP devices.
The method of this embodiment of the present invention may include assigning a first subset of the numerical addresses to a first subset of the mass storage devices mounted in a first chassis in the mounting system. A second subset of the numerical addresses may be assigned to a second subset of the mass storage devices mounted in a second chassis in a second chassis in the mounting system. The assigning of the first and second subsets of the numerical addresses may be based upon (1) an actual configuration of the mass storage devices mounted in the mounting system, and (2) respective addresses assigned to the first chassis and to the second chassis.
Each respective address in the second subset of the numerical addresses may be equal to a respective combination of both a respective corresponding address in the first subset of the numerical addresses and the address assigned to the second chassis. More specifically, each respective address in the second subset of the numerical addresses may be equal to a respective summation of both a respective corresponding address in the first subset of the numerical addresses and the address assigned to the second chassis. The address assigned to the second chassis may be generated by a hardwired connection provided by a special cable connecting the second chassis to a port of a disk adapter. The respective corresponding address may be pre-assigned to a respective connector via which a respective mass storage device is coupled to a back plane in the mounting system.
The first subset of the numerical addresses may comprise only addresses that are greater than or equal to 0 hexadecimal and less than 20 hexadecimal. The second subset of the numerical addresses may comprise only address that are greater than or equal to 20 hexadecimal and less than 40 hexadecimal.
If the actual configuration of the mass storage devices mounted in the mounting system is a first configuration, the mounting system may also include a third chassis and a fourth chassis. When this first configuration of the mass storage devices is mounted in the mounting system, the method of this embodiment may also include the steps of assigning a third subset of the numerical addresses to a third subset of the mass storage devices mounted in the third chassis, and assigning a fourth subset of the numerical address to a fourth subset of the mass storage device mounted in the fourth chassis.
When the first configuration of the mass storage devices is mounted in the mounting system, a first subset of the numerical addresses may include only addresses that are greater than or equal to 0 hexadecimal and less than 20 hexadecimal. The second subset of the numerical addresses may include only addresses that are greater than or equal to 20 hexadecimal and less than 40 hexadecimal. The third subset of the numerical addresses may include only addresses that are greater than or equal to 40 hexadecimal and less than 60 hexadecimal. The fourth subset of the numerical addresses may include only addresses that are greater than or equal to 60 hexadecimal and less than or equal to 7D hexadecimal. In this first configuration of the mass storage devices, the first, second, third, and fourth chassis may mount only disk mass storage devices that have a half height form factor.
Alternatively, in this first configuration, the first, second, third, and fourth chassis may mount respective combinations of mass storage devices. Each of the respective combinations of mass storage devices may include both mass storage devices that have a half height form factor and mass storage devices that have a low profile form factor.
The mass storage devices that are assigned the addresses according to this embodiment of the present invention may communicate with one or more disk controllers via an FC arbitrated loop (AL) network. The addresses that are assigned to the mass storage devices mounted in the mounting system may be FC loop network logical addresses that may used by the one or more disk controllers to facilitate communications with the mass storage devices via the FC communication system.
In this embodiment of the method, FC loop addresses 7E hexadecimal and 7F hexadecimal may be reserved. Thus, as will be appreciated by those skilled in the art, given these address reservations, and the inherent limitations imposed by FC protocol on the maximum number FC devices that may be addressed on a single FC loop, 7D hexadecimal is the maximum FC loop address that may be assigned to a mass storage device that may be coupled to such a FC loop network.
Thus, advantageously, the technique of the present invention may be used to map/assign FC loop addresses to disk mass storage devices mounted in a mounting system of the type of disclosed in the aforesaid copending U.S. patent application Ser. No. 09/877,808, entitled xe2x80x9cMass Storage Device Mounting System,xe2x80x9d filed concurrently with the subject application. Also advantageously, the technique of the present invention may permit a maximum number of such mass storage devices to be useable in a single FC loop.
Depending upon the actual configuration of the mass storage devices in the mounting system, the mass storage devices may be coupled to different chassis back plane connectors and therefore, theological addresses that may be assigned to the mass storage devices may differ depending upon said actual configuration. Furthermore, addresses may be assigned to the mass storage devices based upon the connectors that couple the devices to the mounting system chassis, and the cables that couple the chassis to the disk adapters. Advantageously, this may reduce the possibility that human error and/or addressing conflicts may be introduced into the addresses assigned to the mass storage devices, since the process of assigning the addresses may be substantially automated.
These and other features and advantages of the present invention will become apparent as the following Detailed Description proceeds and upon reference to the Figures of the Drawings, in which like numerals depict like parts, and wherein: